Space-through charge transfer compound, and organic light emitting diode and organic light emitting display device including the same

ABSTRACT

The present disclosure provides a space-through charge transfer compound of following formula and an organic light emitting diode and an organic light emitting display device including the space-through charge transfer compound.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of Republic of KoreaPatent Application No. 10-2018-0067495 filed on Jun. 12, 2018, which ishereby incorporated by reference in its entirety.

BACKGROUND Technical Field

The present disclosure relates to an emitting material and moreparticularly to a space-through charge transfer compound havingexcellent emitting efficiency and an organic light emitting diode (OLED)and an organic light emitting display device including the space-throughcharge transfer compound.

Description of the Related Art

The requirements of the large-size display device have led todevelopments in flat panel display devices as an image display device.Among the flat panel display devices, the OLED has rapidly developed.

In the OLED, when the electron from a cathode, which serves as anelectron-injecting electrode, and the hole from an anode, which servesas a hole-injecting electrode, are injected into an emitting materiallayer, the electron and the hole are combined and become extinct suchthat the light is emitted from the OLED. A flexible substrate, forexample, a plastic substrate, can be used as a base substrate for theOLED, and the OLED has excellent characteristics of driving voltage,power consumption, and color purity.

The OLED includes a first electrode as an anode on a substrate, a secondelectrode as a cathode facing the first electrode, and an organicemitting layer therebetween.

To improve the emitting efficiency, the organic emitting layer mayinclude a hole injection layer (HIL), a hole transporting layer (HTL),an emitting material layer (EML), an electron transporting layer (HTL),and an electron injection layer (EIL) sequentially stacked on the firstelectrode.

The hole is transferred into the EML from the first electrode throughthe HIL and the HTL, and the electron is transferred into the EML fromthe second electrode through the EIL and the ETL.

The electron and the hole are combined in the EML to generated excitons,and the excitons are transited from an excited state to a ground statesuch the light is emitted.

The External quantum efficiency of the emitting material for the EML canbe expressed by the following equation:

η_(ext)=η_(int)×Γ×Φ×η_(out-coupling)

In the above equation, “η_(int)” is the internal quantum efficiency, “Γ”is the charge balance factor, “Φ” is the radiative quantum efficiency,and “η_(out-coupling)” is the out-coupling efficiency.

The charge balance factor “r” means a balance between the hole and theelectron when generating the exciton. Generally, assuming 1:1 matchingof the hole and the electron, the charge balance factor has a value of“1”. The radiative quantum efficiency “Φ” is a value regarding aneffective emitting efficiency of the emitting material. In thehost-dopant system, the radiative quantum efficiency depends on afluorescent quantum efficiency of the dopant.

The internal quantum efficiency “η_(int)” is a ratio of the excitonsgenerating the light to the excitons generated by the combination ofholes and electrons. In the fluorescent compound, a maximum value of theinternal quantum efficiency is 0.25. When the hole and the electron arecombined to generate the exciton, a ratio of the singlet excitons to thetriplet excitons is 1:3 according to the spin structure. However, in thefluorescent compound, only the singlet excitons excluding the tripletexcitons are engaged in emission.

The out-coupling efficiency “η_(out-coupling)” is a ratio of the lightemitted from the display device to the light emitted from the EML. Whenthe isotropic compounds are deposited in a thermal evaporation method toform a thin film, the emitting materials are randomly oriented. In thisinstance, the out-coupling efficiency of the display device may beassumed as 0.2.

Accordingly, the maximum emitting efficiency of the OLED including thefluorescent compound as the emitting material is less than approximately5%.

To overcome the disadvantage of the emitting efficiency of thefluorescent compound, the phosphorescent compound, where both thesinglet excitons and the triplet excitons are engaged in the emission,has been developed for the OLED.

The red and green phosphorescent compounds having a relatively highefficiency are introduced and developed. However, there is no bluephosphorescent compound meeting the requirements in emitting efficiencyand reliability.

BRIEF SUMMARY

Accordingly, the embodiment of the present disclosure is directed to aspace-through charge transfer compound and an OLED and an organic lightemitting display device using the same that substantially obviate one ormore of the problems due to limitations and disadvantages of the relatedart.

An objective of the embodiment of the present disclosure is to provide aspace-through charge transfer compound having high emitting efficiency.

Another objective of the embodiment of the present disclosure is toprovide an OLED and an organic light emitting display device havingimproved emission efficiency.

Additional features and advantages of the disclosure will be set forthin the description which follows, and in part will be apparent from thedescription, or may be learned by practice of the disclosure. Theobjectives and other advantages of the disclosure will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the embodiments of the disclosure, as embodied and broadly describedherein, embodiments relate to a space-through charge transfer compoundof

wherein X is carbon or nitrogen, wherein A is selected from Formula 2,and D is selected from Formula 3:

wherein each of X1, X2 and X3 is independently carbon or nitrogen, andat least one of X1, X2 and X3 is nitrogen, wherein each of R1 and R2 isindependently selected from the group consisting of hydrogen, C1 to C10alkyl group and C6 to C30 aryl group, wherein R3 is cyano group, and R4is heteroaryl group and wherein R5 is selected from the group consistingof hydrogen and heteroaryl group, and each of R6 and R7 is hydrogen orR6 and R7 are bonded together to form a fused ring.

Embodiments also relate to an organic light emitting diode including afirst electrode, a second electrode facing the first electrode, and afirst emitting material layer between the first and second electrodesand including a space-through charge transfer compound.

Embodiments also relate to an organic light emitting display deviceincluding a substrate, an organic light emitting diode on the substrate,and an encapsulation film covering the organic light emitting diode.

It is to be understood that both the foregoing general description andthe following detailed description are by example and explanatory andare intended to provide further explanation of the disclosure asclaimed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 is a view illustrating an emission mechanism of a space-throughcharge transfer compound according to the present disclosure.

FIGS. 2A and 2B are views illustrating charge transfer in aspace-through charge transfer compound according to the presentdisclosure.

FIGS. 3A and 3B are views showing highest occupied molecular orbital(HOMO) distribution and lowest occupied molecular orbital (LUMO)distribution of a space-through charge transfer compound 1 according tothe present disclosure.

FIGS. 4A and 4B are views showing HOMO distribution and LUMOdistribution of a comparative compound 1.

FIGS. 5A and 5B are views showing HOMO distribution and LUMOdistribution of a space-through charge transfer compound 5 according tothe present disclosure.

FIGS. 6A and 6B are views showing HOMO distribution and LUMOdistribution of a comparative compound 2.

FIG. 7 is a schematic cross-sectional view of an organic light emittingdisplay device according to the present disclosure.

FIG. 8 is a schematic cross-sectional view of an organic light emittingdiode (OLED) according to the present disclosure.

FIG. 9 is a schematic cross-sectional view of an OLED according to thepresent disclosure.

FIG. 10 is a schematic cross-sectional view of an OLED according to thepresent disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments, examples ofwhich are illustrated in the accompanying drawings.

A space-through charge transfer compound of the present disclosure has aspiro-xanthane core (or bridge), an electron acceptor moiety, which isbonded (connected) to one of a 4′-positon of the spiro-xanthane core anda 5′-position of the spiro-xanthane, and an electron donor moiety, whichis bonded to the other one of a 4′-positon of the spiro-xanthane coreand a 5′-position of the spiro-xanthane core. The space-through chargetransfer compound may have Formula 1 of the following.

In Formula 1, X is carbon or nitrogen.

In the Formula 1, A as the electron acceptor moiety is selected fromFormula 2.

In the Formula 2, each of X1, X2 and X3 is independently carbon ornitrogen, and at least one of X1, X2 and X3 is nitrogen. In addition,each of R1 and R2 is independently selected from the group consisting ofhydrogen, C1 to C10 alkyl group and C6 to C30 aryl group. For example,each of R1 and R2 may be phenyl. In addition, R3 is cyano group, and R4is heteroaryl group. For example, the heteroaryl group for R4 may bepyridyl or diazinyl.

For example, the electron acceptor moiety A may be selected from Formula3.

In the Formula 1, D as the electron donor moiety is selected fromFormula 4.

In the Formula 4, R5 is selected from the group consisting of hydrogenand heteroaryl group. For example, the heteroaryl group for R5 may becarbazolyl. In addition, each of R6 and R7 is hydrogen or R6 and R7 arebonded together to form a fused ring.

For example, the electron donor moiety D may be selected from Formula 5.

In the space-through charge transfer compound, the electron donor moietyand the electron acceptor moiety are bonded (combined or linked) in themolecule such that an overlap between the highest occupied molecularorbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) isreduced. As a result, a charge transfer complex is generated, and theemitting efficiency of the space-through charge transfer compound isimproved. Namely, in the space-through charge transfer compound, thetriplet exciton is used for emission such that the emitting efficiencyis improved.

In other words, since the space-through charge transfer compound of thepresent disclosure includes both of the electron donor moiety and theelectron acceptor moiety, the charge is easily transferred in themolecule, and emission efficiency is improved.

In the space-through charge transfer compound of the present disclosure,since the electron donor moiety and the electron acceptor moiety areboned to the 4′-position and the 5′-position of the spiro-xanthane core,respectively, a gap or a distance between the electron donor moiety andthe electron acceptor moiety is decreased or minimized. Accordingly, thecharge transfer is directly generated through a space between theelectron donor moiety and the electron acceptor moiety such that theconjugation length in the space-through charge transfer compound becomesshorter than another compound where the charge transfer is generatedthrough a bonding orbital. As a result, a red shift problem in theemitted light can be prevented, and the space-through charge transfercompound of the present disclosure can provide deep blue emission.

Referring to FIG. 1, which is a view illustrating an emission mechanismof a space-through charge transfer compound according to the presentdisclosure, in the space-through charge transfer compound of the presentdisclosure, the triplet excitons as well as the singlet excitons areengaged in the emission such that the emitting efficiency is improved.

Namely, the triplet exciton is activated by a field or heat, and thetriplet exciton and the singlet exciton are transferred into anintermediated state “I₁” and transited into a ground state “So” to emitthe light. In other words, the singlet state “S₁” and the triplet state“T₁” are transited into the intermediated state “I₁” (S₁->I₁<−T₁), andthe singlet exciton and the triplet exciton in the intermediated state“I₁” are engaged in the emission such that the emitting efficiency isimproved. The compound having the above emission mechanism may bereferred to as a field activated delayed fluorescence (FADF) compound ora thermally activated delayed fluorescence (TADF) compound.

In the related art fluorescence compound, since the HOMO and the LUMOare dispersed throughout an entirety of the molecule, theinterconversion of the HOMO and the LUMO is impossible. (SelectionRule.)

However, in the FADF compound, since the overlap between the HOMO andthe LUMO in the molecule is relatively small, the interaction betweenthe HOMO and the LUMO is small. Accordingly, changes of the spin stateof one electron do not affect other electrons, and a new charge transferband, which does not comply with the Selection Rule, is generated.

Moreover, since the electron donor moiety and the electron acceptormoiety is spatially spaced apart from each other in the molecule, thedipole moment is generated in a polarized state. In the polarized statedipole moment, the interaction between the HOMO and the LUMO is furtherreduced such that the emission mechanism does not comply with theSelection Rule. Accordingly, in the FADF compound or the TADF compound,the transition from the triplet state “T₁” and the singlet state “S₁”into the intermediated state “I₁” can be generated such that the tripletexciton can be engaged in the emission.

When the OLED is driven, the intersystem transition (intersystemcrossing) from 25% singlet state “S₁” excitons and 75% triplet state“T₁” excitons to the intermediated state “I₁” is generated, and thesinglet and triplet excitons in the intermediated state “I₁” aretransited into the ground state to emit the light. As a result, the FADFcompound has the theoretic quantum efficiency of 100%.

For example, the space-through charge transfer compound in Formula 1 maybe one of compounds in Formula 6.

The space-through charge transfer compound of the present disclosure hasa wide energy band gap such that the emission efficiency of the OLEDusing the compound is improved.

The space-through charge transfer compound of the present disclosure hasan energy bandgap, i.e., a difference between an energy level of theHOMO and an energy level of the LUMO, above about 3.6 eV. For example,the energy bandgap of the space-through charge transfer compound mayhave a range of about 3.6 to 3.8 eV.

The HOMO distribution and the LUMO distribution of the compound 1 in theFormula 6 is shown in FIGS. 3A and 3B, and the HOMO distribution and theLUMO distribution of a comparative compound 1 of Formula 7 is shown inFIGS. 4A and 4B. The HOMO distribution and the LUMO distribution of thecompound 5 in the Formula 6 is shown in FIGS. 5A and 5B, and the HOMOdistribution and the LUMO distribution of a comparative compound 2 ofFormula 8 is shown in FIGS. 6A and 6B. The energy level of HOMO, theenergy level LUMO and the energy bandgap (Eg) of the compounds 1 and 13and the comparative compounds 1 and 2 are listed in Table 1.

TABLE 1 HOMO LUMO Eg Compound1 5.22 1.61 3.61 Comparative 5.22 1.89 3.33compound1 Compound5 5.22 1.47 3.75 Comparative 5.17 1.77 3.4 compound2

As shown in FIGS. 3A to 6B and Table 1, in the space-through chargetransfer compound of the present disclosure, the HOMO and the LUMO areeasily separated, and the energy bandgap is above 3.6 eV. Accordingly,in the space-through charge transfer compound of the present disclosure,the triplet exciton is engaged in the emission such that the emittingefficiency is improved and the deep blue emission is provided.

Synthesis

Synthesis of Compound 1

In the rounded-bottom flask (500 ml), fluorenone (180.06 g/mol) and4-bromophenol (171.95 g/mol) were added in chloroform (200 ml) and theN₂ gas is purged. Methanesulfonic acid was slowly dropped into themixture and stirred under the room temperature for 24 hrs. Aftercompletion of the reaction, the organic layer was extracted usingdichloromethane and distilled water, and the solvent was removed by areduced-pressure distillation. The column chromatography using thedeveloping solvent of hexane and ethylacetate (9:1) is performed suchthat the compound A of white solid was obtained.

In the N₂ gas purging system, the compound B and butyl-lithium (BuLi,1.5 equivalent) were added into ether, and the mixture was stirred underthe temperature of −78° C. After the mixture was reacted for 2 hrs,trimethyl borate (1.2 equivalent) was added, and the mixture was stirredunder the temperature of −78° C. for 30 minutes. The mixture was reactedunder the room temperature for 8 hrs. HCl in DI water (30 ml) was added,and the organic solvent was removed. The residual was filtered such thatthe compound C in white solid was obtained.

In the N₂ gas purging system, the compound A, carbazole (0.4equivalent), tris(dibenzylideneacetone)dipalladium(0) (0.1 equivalent),triphenylphosphine (0.2 equivalent) and sodium tert-butoxide (4.0equivalent) were added in toluene, and the mixture was stirred in theoil bath under the temperature of 100° C. for 16 hrs. Water was addedinto the mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and methylenechloride (2:1) is performedsuch that the compound D of white solid was obtained.

In the N₂ gas purging system, the compound D, the compound C (1.3equivalent), Pd(0) (0.1 equivalent) and potassium carbonate (4.0equivalent) was added in toluene, and the mixture was stirred in the oilbath under the temperature of 80° C. for 24 hrs. Water was added intothe mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and ethylacetate (6:1) is performed suchthat the compound 1 of white solid was obtained.

Synthesis of Compound 2

In the N₂ gas purging system, the compound A, spiroacridine (0.5equivalent), tris(dibenzylideneacetone)dipalladium(0) (0.11 equivalent),triphenylphosphine (0.2 equivalent) and sodium tert-butoxide (4.0equivalent) were added in toluene, and the mixture was stirred in theoil bath under the temperature of 90° C. for 14 hrs. Water was addedinto the mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and methylenechloride (3:1) is performedsuch that the compound E of white solid was obtained.

In the N₂ gas purging system, the compound E, the compound C (1.2equivalent), Pd(0) (0.1 equivalent) and potassium carbonate (4.0equivalent) was added in toluene, and the mixture was stirred in the oilbath under the temperature of 80° C. for 16 hrs. Water was added intothe mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and ethylacetate (7:1) is performed suchthat the compound 2 of white solid was obtained.

Synthesis of Compound 3

In the N₂ gas purging system, the compound A, dimethylacridine (0.35equivalent), tris(dibenzylideneacetone)dipalladium(0) (0.1 equivalent),triphenylphosphine (0.2 equivalent) and sodium tert-butoxide (4.0equivalent) were added in toluene, and the mixture was stirred in theoil bath under the temperature of 100° C. for 12 hrs. Water was addedinto the mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and methylenechloride (5:1) is performedsuch that the compound F of white solid was obtained.

In the N₂ gas purging system, the compound F, the compound C (1.2equivalent), Pd(0) (0.1 equivalent) and potassium carbonate (4.0equivalent) was added in toluene, and the mixture was stirred in the oilbath under the temperature of 80° C. for 18 hrs. Water was added intothe mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and ethylacetate (5:1) is performed suchthat the compound 3 of white solid was obtained.

Synthesis of Compound 5

In the N₂ gas purging system, the compound G and BuLi (1.5 equivalent)were added into ether, and the mixture was stirred under the temperatureof −78° C. After the mixture was reacted for 2 hrs, trimethyl borate(1.2 equivalent) was added, and the mixture was stirred under thetemperature of −78° C. for 30 minutes. The mixture was reacted under theroom temperature for 14 hrs. HCl in DI water (30 ml) was added, and theorganic solvent was removed. The residual was filtered such that thecompound H in white solid was obtained.

In the N₂ gas purging system, the compound D, the compound H (1.4equivalent), Pd(0) (0.1 equivalent) and potassium carbonate (4.0equivalent) was added in toluene, and the mixture was stirred in the oilbath under the temperature of 80° C. for 18 hrs. Water was added intothe mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and ethylacetate (9:1) is performed suchthat the compound 5 of white solid was obtained.

Synthesis of Compound 9

In the N₂ gas purging system, the compound I and BuLi (1.5 equivalent)were added into ether, and the mixture was stirred under the temperatureof −78° C. After the mixture was reacted for 1 hr, trimethyl borate (1.2equivalent) was added, and the mixture was stirred under the temperatureof −78° C. for 30 minutes. The mixture was reacted under the roomtemperature for 12 hrs. HCl in DI water (30 ml) was added, and theorganic solvent was removed. The residual was filtered such that thecompound J in white solid was obtained.

In the N₂ gas purging system, the compound J, the compound K (2.1equivalent), Pd(0) (0.1 equivalent) and potassium carbonate (4.0equivalent) was added in toluene, and the mixture was stirred in the oilbath under the temperature of 80° C. for 10 hrs. Water was added intothe mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and methylenechloride (5:1) is performedsuch that the compound L of white solid was obtained.

In the N₂ gas purging system, the compound L and BuLi (1.5 equivalent)were added into ether, and the mixture was stirred under the temperatureof −78° C. After the mixture was reacted for 30 minutes, trimethylborate (1.2 equivalent) was added, and the mixture was stirred under thetemperature of −78° C. for 1 hr. The mixture was reacted under the roomtemperature for 20 hrs. HCl in DI water (20 ml) was added, and theorganic solvent was removed. The residual was filtered such that thecompound M in white solid was obtained.

In the N₂ gas purging system, the compound D, the compound M (1.3equivalent), Pd(0) (0.1 equivalent) and potassium carbonate (4.0equivalent) was added in toluene, and the mixture was stirred in the oilbath under the temperature of 100° C. for 24 hrs. Water was added intothe mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and ethylacetate (10:1) is performed suchthat the compound 9 of white solid was obtained.

Synthesis of Compound 25

In the N₂ gas purging system, the compound N and the compound O (1.1equivalent) were dissolved in the tetrahydrofuran (THF) solvent, and hemixture was cooled into −78° C. BuLi (1.1 equivalent) was dropped intothe mixture and stirred for 1 hr. After the mixture was heated into −70°C., HCl (10 ml) and acetic acid aqueous solution (10 ml) were added. Themixture was stirred under the temperature of 70° C. for 8 hrs. Water wasslowly added to finish the reaction and extract. The columnchromatography using the developing solvent of hexane andmethylenechloride (5:1) is performed such that the compound P of whitesolid was obtained.

In the N₂ gas purging system, the compound P, carbazole (0.5equivalent), tris(dibenzylideneacetone)dipalladium(0) (0.1 equivalent),triphenylphosphine (0.2 equivalent) and sodium tert-butoxide (4.0equivalent) were added in toluene, and the mixture was stirred in theoil bath under the temperature of 80° C. for 13 hrs. Water was addedinto the mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and methylenechloride (3:1) is performedsuch that the compound Q of white solid was obtained.

In the N₂ gas purging system, the compound Q, the compound C (1.2equivalent), Pd(0) (0.1 equivalent) and potassium carbonate (4.0equivalent) was added in toluene, and the mixture was stirred in the oilbath under the temperature of 100° C. for 36 hrs. Water was added intothe mixture and was extracted. The column chromatography using thedeveloping solvent of hexane and ethylacetate (10:1) is performed suchthat the compound 25 of white solid was obtained.

In the space-through charge transfer compound of the present disclosure,the 25% excitons in the singlet state and the 75% excitons in thetriplet state are transited into the intermediate state by an outerforce, i.e., a field generated when the OLED is driven. (Intersystemcrossing.) The excitons in the intermediate state are transited into theground state such that the emitting efficiency is improved. Namely, inthe fluorescent compound, since the singlet exciton and the tripletexciton are engaged in emission, the emitting efficiency is improved.

OLED

An ITO layer is deposited on a substrate and washed to form an anode (3mm*3 mm). The substrate is loaded in a vacuum chamber, and a holeinjecting layer, a hole transporting layer, an emitting material layer,an electron transporting layer, an electron injecting layer, and acathode (Al) are sequentially formed on the anode under a base pressureof about 10⁻⁶ to 10⁻⁷ Torr. The emitting material layer is formed usinga host of a material in Formula 9 and a dopant (30 wt %).

Example 1 (Ex1)

The compound 1 in Formula 6 is used as the dopant in the emittingmaterial layer.

Example 2 (Ex2)

The compound 5 in Formula 6 is used as the dopant in the emittingmaterial layer.

Example 3 (Ex3)

The compound 2 in Formula 6 is used as the dopant in the emittingmaterial layer.

Example 4 (Ex4)

The compound 25 in Formula 6 is used as the dopant in the emittingmaterial layer.

Comparative Example 1 (Ref1)

The compound in Formula 7 is used as the dopant in the emitting materiallayer.

Comparative Example 2 (Ref2)

The compound in Formula 8 is used as the dopant in the emitting materiallayer.

The properties, i.e., a PL maximum value (PL_(max), nm), an extinctiontime of an emitting exciton (Tau, μs), voltate (V), current efficiency(cd/A), power efficiency (lm/W), external quantum efficiency (EQE, %),color coordinate index (CIE(X), CIE(Y)), lifespan (T95, hr), of the OLEDin Examples 1 to 4 and Comparative Examples 1 and 2 are measured andlisted in Table 2. The lifespan is a time taking the brightness from theinitial brightness (300 nit) into 95%.

TABLE 2 CIE CIE PL_(max) Tau V cd/A lm/W EQE (X) (Y) T95 Ex1 455 5.63.73 24.08 20.27 13.23 0.152 0.220 42 Ex2 452 7.8 3.75 25.11 21.02 14.090.157 0.232 53 Ex3 453 4.3 3.81 25.43 20.96 14.28 0.156 0.219 49 Ex4 4602.5 3.76 26.87 22.44 15.83 0.158 0.232 70 Ref1 471 2.3 3.89 23.97 19.3513.17 0.152 0.217 6.0 Ref2 468 3.1 3.77 23.03 19.18 12.85 0.156 0.2215.5

As shown in Table 2, in comparison to the OLED of Comparative Examples 1and 2, the OLED including the space-through charge transfer compound ofthe present disclosure has high emitting efficiency and long lifespanand provides a deep blue emission.

For example, the compounds 1 and 5 of Formula 6 and the comparativecompounds 1 and 2 of Formulas 7 and 8 have a difference in a bondingposition of the electron donor moiety, and a distance between theelectron acceptor moiety and the electron donor moiety in the compounds1 and 5 is decreased. Accordingly, the charge transfer property througha space between the electron donor moiety and the electron acceptormoiety is improved such that the space-through charge transfer compoundof the present disclosure has advantages of high emitting efficiency,long lifespan and deep blue emission.

In addition, since the extinction time of the emitting exciton isseveral micro seconds, the space-through charge transfer compound of thepresent disclosure has a delayed fluorescence property. Generalfluorescence material has the extinction time of several nano-seconds.

FIG. 7 is a schematic cross-sectional view of an organic light emittingdisplay device according to the present disclosure.

As shown in FIG. 7, the OLED device 100 includes a substrate 110, a thinfilm transistor (TFT) Tr and an organic light emitting diode D connectedto the TFT Tr.

The substrate 110 may be a glass substrate or a plastic substrate. Forexample, the substrate 110 may be a polyimide substrate.

A buffer layer 120 is formed on the substrate, and the TFT Tr is formedon the buffer layer 120. The buffer layer 120 may be omitted.

A semiconductor layer 122 is formed on the buffer layer 120. Thesemiconductor layer 122 may include an oxide semiconductor material orpolycrystalline silicon.

When the semiconductor layer 122 includes the oxide semiconductormaterial, a light-shielding pattern (not shown) may be formed under thesemiconductor layer 122. The light to the semiconductor layer 122 isshielded or blocked by the light-shielding pattern such that thermaldegradation of the semiconductor layer 122 can be prevented. On theother hand, when the semiconductor layer 122 includes polycrystallinesilicon, impurities may be doped into both sides of the semiconductorlayer 122.

A gate insulating layer 124 is formed on the semiconductor layer 122.The gate insulating layer 124 may be formed of an inorganic insulatingmaterial such as silicon oxide or silicon nitride.

A gate electrode 130, which is formed of a conductive material, e.g.,metal, is formed on the gate insulating layer 124 to correspond to acenter of the semiconductor layer 122.

In FIG. 7, the gate insulating layer 124 is formed on an entire surfaceof the substrate 110. Alternatively, the gate insulating layer 124 maybe patterned to have the same shape as the gate electrode 130.

An interlayer insulating layer 132, which is formed of an insulatingmaterial, is formed on the gate electrode 130. The interlayer insulatinglayer 132 may be formed of an inorganic insulating material, e.g.,silicon oxide or silicon nitride, or an organic insulating material,e.g., benzocyclobutene or photo-acryl.

The interlayer insulating layer 132 includes first and second contactholes 134 and 136 exposing both sides of the semiconductor layer 122.The first and second contact holes 134 and 136 are positioned at bothsides of the gate electrode 130 to be spaced apart from the gateelectrode 130.

The first and second contact holes 134 and 136 are formed through thegate insulating layer 124. Alternatively, when the gate insulating layer124 is patterned to have the same shape as the gate electrode 130, thefirst and second contact holes 134 and 136 is formed only through theinterlayer insulating layer 132.

A source electrode 140 and a drain electrode 142, which are formed of aconductive material, e.g., metal, are formed on the interlayerinsulating layer 132.

The source electrode 140 and the drain electrode 142 are spaced apartfrom each other with respect to the gate electrode 130 and respectivelycontact both sides of the semiconductor layer 122 through the first andsecond contact holes 134 and 136.

The semiconductor layer 122, the gate electrode 130, the sourceelectrode 140 and the drain electrode 142 constitute the TFT Tr. The TFTTr serves as a driving element.

In the TFT Tr, the gate electrode 130, the source electrode 140, and thedrain electrode 142 are positioned over the semiconductor layer 122.Namely, the TFT Tr has a coplanar structure.

Alternatively, in the TFT Tr, the gate electrode may be positioned underthe semiconductor layer, and the source and drain electrodes may bepositioned over the semiconductor layer such that the TFT Tr may have aninverted staggered structure. In this instance, the semiconductor layermay include amorphous silicon.

Although not shown, the gate line and the data line cross each other todefine the pixel region, and the switching TFT is formed to be connectedto the gate and data lines. The switching TFT is connected to the TFT Tras the driving element.

In addition, the power line, which may be formed to be parallel to andspaced apart from one of the gate and data lines, and the storagecapacitor for maintaining the voltage of the gate electrode of the TFTTr in one frame may be further formed.

A passivation layer 150, which includes a drain contact hole 152exposing the drain electrode 142 of the TFT Tr, is formed to cover theTFT Tr.

A first electrode 160, which is connected to the drain electrode 142 ofthe TFT Tr through the drain contact hole 152, is separately formed ineach pixel region. The first electrode 160 may be an anode and may beformed of a conductive material having a relatively high work function.For example, the first electrode 160 may be formed of a transparentconductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide(IZO).

When the OLED device 100 is operated in a top-emission type, areflection electrode or a reflection layer may be formed under the firstelectrode 160. For example, the reflection electrode or the reflectionlayer may be formed of aluminum-palladium-copper (APC) alloy.

A bank layer 166 is formed on the passivation layer 150 to cover an edgeof the first electrode 160. Namely, the bank layer 166 is positioned ata boundary of the pixel region and exposes a center of the firstelectrode 160 in the pixel region.

An organic emitting layer 162 is formed on the first electrode 160. Theorganic emitting layer 162 includes the space-through charge transfercompound of Formula 1. The space-through charge transfer compound may beused as a dopant, and the organic emitting layer 162 may further includea host. For example, the dopant may have a weight % of about 1 to 30with respect to the host. The organic emitting layer 162 provides bluelight.

The organic emitting layer 162 may have a single-layered structure of anemitting material layer including an emitting material. To increase anemitting efficiency of the OLED device, the organic emitting layer 162may have a multi-layered structure.

A second electrode 164 is formed over the substrate 110 where theorganic emitting layer 162 is formed. The second electrode 164 covers anentire surface of the display area and may be formed of a conductivematerial having a relatively low work function to serve as a cathode.For example, the second electrode 164 may be formed of aluminum (Al),magnesium (Mg) or Al—Mg alloy.

The first electrode 160, the organic emitting layer 162 and the secondelectrode 164 constitute the organic light emitting diode D.

An encapsulation film 170 is formed on the second electrode 164 toprevent penetration of moisture into the organic light emitting diode D.The encapsulation film 170 includes a first inorganic insulating layer172, an organic insulating layer 174 and a second inorganic insulatinglayer 176 sequentially stacked, but it is not limited thereto.

A polarization plate (not shown) for reducing an ambient lightreflection may be disposed over the top-emission type organic lightemitting diode D. For example, the polarization plate may be a circularpolarization plate.

In addition, a cover window (not shown) may be attached to theencapsulation film 170 or the polarization plate. In this instance, thesubstrate 110 and the cover window have a flexible property such that aflexible OLED device may be provided.

FIG. 8 is a schematic cross-sectional view of an organic light emittingdiode (OLED) according to the present disclosure.

As shown in FIG. 8, the organic light emitting diode D includes thefirst and second electrodes 160 and 164, which face each other, and theorganic emitting layer 162 therebetween. The organic emitting layer 162includes an emitting material layer (EML) 240 between the first andsecond electrodes 160 and 164, a hole transporting layer (HTL) 220between the first electrode 160 and the EML 240 and an electrontransporting layer (ETL) 260 between the second electrode 164 and theEML 240.

In addition, the organic emitting layer 162 may further include a holeinjection layer (HIL) 210 between the first electrode 160 and the HTL220 and an electron injection layer (EIL) 270 between the secondelectrode 164 and the ETL 260.

Moreover, the organic emitting layer 162 may further include an electronblocking layer (EBL) 230 between the HTL 220 and the EML 240 and a holeblocking layer (HBL) 250 between the EML 240 and the ETL 260.

The EML 240 includes the space-through charge transfer compound ofFormula 1 as a dopant and may further include a host.

A difference between an energy level of the HOMO of the host“HOMO_(Host)” and an energy level of the HOMO of the dopant“HOMO_(Dopant)” or a difference between an energy level of the LUMO ofthe host “LUMO_(Host)” and an energy level of the LUMO of the dopant“LUMO_(Dopant)” is less than about 0.5 eV. In this instance, the chargetransfer efficiency from the host to the dopant may be improved.

The energy level of triplet state of the dopant is smaller than theenergy level of triplet state of the host, and a difference between theenergy level of singlet state of the dopant and the energy level oftriplet state of the dopant is equal to less than 0.3 eV. (ΔE_(ST)≤0.3eV.) As the difference “ΔE_(ST)” is smaller, the emitting efficiency ishigher. In addition, even if the difference “ΔE_(ST)” between the energylevel of singlet state of the dopant and the energy level of tripletstate of the dopant is about 0.3 eV, which is relatively large, theexcitons in the singlet state and the excitons in the triplet state canbe transited into the intermediate state.

For example, the host, which meets the above condition, may be selectedfrom materials in Formula 10. (Bis[2-(diphenylphosphino)phenyl]etheroxide (DPEPO), 2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT),2,8-di(9H-carbazol-9-yl)dibenzothiophene (DCzDBT),m-bis(carbazol-9-yl)biphenyl (m-CBP),Diphenyl-4-triphenylsilylphenyl-phosphine oxide (TPSO1),9-(9-phenyl-9H-carbazol-6-yl)-9H-carbazole (CCP) in order.)

On the other hand, the space-through charge transfer compound of thepresent disclosure may act as a host in the EML 240, and the EML 240 mayfurther include a dopant to emit the blue light. In this instance, thedopant has about 1 to 30 weight % with respect to the host. Since thedevelopment of the blue host having excellent properties isinsufficient, the space-through charge transfer compound of the presentdisclosure may be used as the host to increase the degree of freedom forthe host. In this instance, the energy level of triplet state of thedopant may be smaller than the energy level of triplet state of the hostof the space-through charge transfer compound of the present disclosure.

The EML 240 may include a first dopant of the space-through chargetransfer compound of the present disclosure, a host, and a seconddopant. The weight % summation of the first and second dopants may beabout 1 to 30 to emit the blue light. The second dopant may be afluorescence material (compound). In this instance, the emittingefficiency and the color purity may be further improved.

An energy level of singlet state of the first dopant (the space-throughcharge transfer compound) is greater than that of the second dopant. Anenergy level of triplet state of the first dopant is smaller than thatof the host and greater than that of the second dopant.

In this instance, the energy level of triplet state of the first dopant,i.e., the space-through charge transfer compound of the presentdisclosure, may be smaller than the energy level of triplet state of thehost and larger than the energy level of triplet state of the seconddopant. In addition, a difference between the energy level of singletstate of the first dopant and the energy level of triplet state of thefirst dopant is less than 0.3 eV. (ΔE_(ST)≤0.3 eV) As the difference“ΔE_(ST)” is smaller, the emitting efficiency is higher. In thespace-through charge transfer compound of the present disclosure, evenif the difference “ΔE_(ST)” between the energy level of singlet state ofthe dopant and the energy level of triplet state of the dopant is about0.3 eV, which is relatively large, the excitons in the singlet state“S₁” and the excitons in the triplet state “T₁” can be transited intothe intermediate state “I₁”.

As mentioned above, in the space-through charge transfer compound of thepresent disclosure, since the electron donor moiety and the electronacceptor moiety are bonded to the spiro-xanthane core in one moleculeand the overlap between the HOMO and the LUMO is decreased, thespace-through charge transfer compound of the present disclosure acts asa charge transfer complex such that the emitting efficiency of thecompound is improved. Namely, in the space-through charge transfercompound of the present disclosure, the excitons in the triplet stateare engaged in the emission such that the emitting efficiency of thecompound is improved.

Since the electron donor moiety and the electron acceptor moiety areboned to the 4′-position and the 5′-position of the spiro-xanthane core,respectively, a gap or a distance between the electron donor moiety andthe electron acceptor moiety is decreased or minimized. Accordingly, thecharge transfer is directly generated through a space between theelectron donor moiety and the electron acceptor moiety such that theconjugation length in the space-through charge transfer compound becomesshorter than another compound where the charge transfer is generatedthrough a bonding orbital. As a result, a red shift problem in theemitted light can be prevented, and the space-through charge transfercompound of the present disclosure can provide deep blue emission.

As a result, the OLED and the organic light emitting display deviceincluding the space-through charge transfer compound has high emittingefficiency and lifespan and provides high quality image.

FIG. 9 is a schematic cross-sectional view of an organic light emittingdiode (OLED) according to the present disclosure.

As shown in FIG. 9, an organic light emitting diode D includes the firstand second electrodes 160 and 164, which face each other, and theorganic emitting layer 162 therebetween. The organic emitting layer 162includes an EML 340, which includes first and second layers 342 and 344and is positioned between the first and second electrodes 160 and 164, aHTL 320 between the first electrode 160 and the EML 340 and an ETL 360between the second electrode 164 and the EML 340.

In addition, the organic emitting layer 162 may further include a HIL310 between the first electrode 160 and the HTL 320 and an EIL 370between the second electrode 164 and the ETL 360.

Moreover, the organic emitting layer 162 may further include an EBL 330between the HTL 320 and the EML 340 and a HBL 350 between the EML 340and the ETL 360.

In the EML 340, one of the first and second layers 342 and 344 includesthe space-through charge transfer compound of the present disclosure asa dopant, and the other one of the first and second layers 342 and 344includes a fluorescence material as a dopant. An energy level of singletstate of the space-through charge transfer compound is greater than thatof the fluorescence material.

The organic light emitting diode, where the first layer 342 includes thespace-through charge transfer compound and the second layer 344 includesthe fluorescent dopant, will be explained.

In the organic light emitting diode D, the energy level of singlet stateand the energy level of triplet state of the space-through chargetransfer compound are transferred into the fluorescence material suchthat the emission is generated from the fluorescence material.Accordingly, the quantum efficiency of the organic light emitting diodeD is increased, and the full width at half maximum (FWHM) of the organiclight emitting diode D is narrowed.

The space-through charge transfer compound having a delayed fluorescenceproperty has high quantum efficiency. However, since the light emittedfrom the space-through charge transfer compound has wide FWHM, the lightfrom the space-through charge transfer compound has poor color purity.On the other hand, the fluorescence material has narrow FWHM and highcolor purity. However, since the energy level of triplet state of thefluorescence material is not engaged in the emission, the fluorescencematerial has low quantum efficiency.

Since the EML 340 of the organic light emitting diode D in the presentdisclosure includes the first layer 342, which includes space-throughcharge transfer compound as the dopant, and the second layer 344, whichincludes the fluorescence material as the dopant, the organic lightemitting diode D has advantages in both the emitting efficiency and thecolor purity.

The energy level of triplet state of the space-through charge transfercompound is converted into the energy level of singlet state of thespace-through charge transfer compound by the reverse intersystemcrossing (RISC) effect, and the energy level of singlet state of thespace-through charge transfer compound is transferred into the energylevel of singlet state of the fluorescence material. Namely, thedifference between the energy level of triplet state of thespace-through charge transfer compound and the energy level of singletstate of the space-through charge transfer compound is not greater than0.3 eV such that the energy level of triplet state of the space-throughcharge transfer compound is converted into the energy level of singletstate of the space-through charge transfer compound by the RISC effect.

As a result, the space-through charge transfer compound has an energytransfer function, and the first layer 342 including the space-throughcharge transfer compound is not engaged in the emission. The emission isgenerated in the second layer 344 including the fluorescence material.

The energy level of triplet state of the space-through charge transfercompound is converted into the energy level of singlet state of thespace-through charge transfer compound by the RISC effect. In addition,since the energy level of singlet state of the space-through chargetransfer compound is higher than that of the fluorescence material, theenergy level of singlet state of the space-through charge transfercompound is transferred into the energy level of singlet state of thefluorescence material. As a result, the fluorescence material emits thelight using the energy level of singlet state and the energy level oftriplet state such that the quantum efficiency (emitting efficiency) ofthe organic light emitting diode D is improved.

In other words, the organic light emitting diode D and the OLED device100 (of FIG. 7) including the organic light emitting diode D hasadvantages in both the emitting efficiency and the color purity.

The first and second layers 342 and 344 may further includes first andsecond hosts, respectively. The first and second hosts may have apercentage by weight being larger than the space-through charge transfercompound and the fluorescence material, respectively. In addition, thepercentage by weight of the space-through charge transfer compound inthe first layer 342 may be greater than that of the fluorescencematerial in the second layer 344. As a result, the energy transfer fromthe space-through charge transfer compound into the fluorescencematerial is sufficiently generated.

The energy level of singlet state of the first host is greater than thatof the space-through charge transfer compound (first dopant), and theenergy level of triplet state of the first host is greater than that ofthe space-through charge transfer compound. In addition, the energylevel of singlet state of the second host is greater than that of thefluorescence material (second dopant).

When not satisfying this condition, a quenching happens at the first andsecond dopants or an energy transfer from the host to the dopant doesnot happen, and thus the quantum efficiency of the organic lightemitting diode D is reduced.

For example, the second host, which is included in the second layer 344with the fluorescence material, may be same as a material of the HBL350. In this instance, the second layer 344 may have a hole blockingfunction with an emission function. Namely, the second layer 344 mayserve as a buffer layer for blocking the hole. When the HBL 350 isomitted, the second layer 344 serves as an emitting layer and a holeblocking layer.

When the first layer 342 includes the fluorescence dopant and the secondlayer 344 includes the space-through charge transfer compound, the firsthost of the first layer 342 may be same as a material of the EBL 330. Inthis instance, the first layer 342 may have an electron blockingfunction with an emission function. Namely, the first layer 342 mayserve as a buffer layer for blocking the electron. When the EBL 330 isomitted, the first layer 342 serves as an emitting layer and an electronblocking layer.

FIG. 10 is a schematic cross-sectional view of an organic light emittingdiode (OLED) according to the present disclosure.

As shown in FIG. 10, an organic light emitting diode D includes thefirst and second electrodes 160 and 164, which face each other, and theorganic emitting layer 162 therebetween. The organic emitting layer 162includes an EML 440, which includes first to third layers 442, 444 and446 and is positioned between the first and second electrodes 160 and164, a HTL 420 between the first electrode 160 and the EML 440 and anETL 460 between the second electrode 164 and the EML 440.

In addition, the organic emitting layer 162 may further include a HIL410 between the first electrode 160 and the HTL 420 and an EIL 470between the second electrode 164 and the ETL 460.

Moreover, the organic emitting layer 162 may further include an EBL 430between the HTL 420 and the EML 440 and a HBL 450 between the EML 440and the ETL 460.

In the EML 440, the first layer 442 is positioned between the secondlayer 444 and the third layer 446. Namely, the second layer 444 ispositioned between the EBL 430 and the first layer 442, and the thirdlayer 446 is positioned between the first layer 442 and the HBL 450.

The first layer 442 (e.g., a first emitting material layer) may includethe space-through charge transfer compound of the present disclosure asa dopant, and each of the second layer 344 (e.g., a second emittingmaterial layer) and the third layer 446 (e.g., a third emitting materiallayer) may include the fluorescence material as a dopant. Thefluorescence material in the second and third layers 444 and 446 may besame or different. The space-through charge transfer compound has anenergy level of singlet state being larger than the fluorescencematerial.

In the organic light emitting diode D, the energy level of singlet stateand the energy level of triplet state of the space-through chargetransfer compound in the first layer 442 are transferred into thefluorescence material in the second layer 444 and/or the third layer 446such that the emission is generated from the fluorescence material. As aresult, the quantum efficiency of the OLED D is increased, and the FWHMof the OLED is narrowed.

The first to third layers 442, 444 and 446 may further include first tothird host, respectively. The first to third hosts are same material ordifferent materials. For example, each of the first to third hosts maybe selected from materials of Formula 10.

In each of the first to third layers 442, 444 and 446, the first tothird hosts may have a percentage by weight being larger than thespace-through charge transfer compound and the fluorescence material,respectively. In addition, the percentage by weight of the space-throughcharge transfer compound (i.e., the first dopant) in the first layer 442may be greater than that of each of the fluorescence material (i.e., thesecond dopant) in the second layer 444 and the fluorescence material(i.e., the third dopant) in the third layer 446.

The energy level of singlet state of the first host is greater than thatof the space-through charge transfer compound, and the energy level oftriplet state of the first host is greater than that of thespace-through charge transfer compound. In addition, the energy level ofsinglet state of the second host is greater than that of thefluorescence material in the second layer 444, and the energy level ofsinglet state of the third host is greater than that of the fluorescencematerial in the third layer 446.

For example, the second host in the second layer 444 may be same as amaterial of the EBL 430. In this instance, the second layer 444 may havean electron blocking function with an emission function. Namely, thesecond layer 444 may serve as a buffer layer for blocking the electron.When the EBL 430 is omitted, the second layer 444 serves as an emittinglayer and an electron blocking layer.

The third host in the third layer 446 may be same as a material of theHBL 450. In this instance, the third layer 446 may have a hole blockingfunction with an emission function. Namely, the third layer 446 mayserve as a buffer layer for blocking the hole. When the HBL 450 isomitted, the third layer 446 serves as an emitting layer and a holeblocking layer.

The second host in the second layer 444 may be same as a material of theEBL 430, and the third host in the third layer 446 may be same as amaterial of the HBL 450. In this instance, the second layer 444 may havean electron blocking function with an emission function, and the thirdlayer 446 may have a hole blocking function with an emission function.Namely, the second layer 444 may serve as a buffer layer for blockingthe electron, and the third layer 446 may serve as a buffer layer forblocking the hole. When the EBL 430 and the HBL 450 are omitted, thesecond layer 444 serves as an emitting layer and an electron blockinglayer and the third layer 446 serves as an emitting layer and a holeblocking layer.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the embodiment of the tripledisclosure without departing from the spirit or scope of the disclosure.Thus, it is intended that the embodiment of the disclosure cover themodifications and variations of this disclosure provided they comewithin the scope of the appended claims and their equivalents.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

What is claimed is:
 1. A space-through charge transfer compound ofFormula 1:

wherein X is carbon or nitrogen, wherein A is selected from Formula 2,and D is selected from Formula 3:

wherein each of X1, X2 and X3 is independently carbon or nitrogen, andat least one of X1, X2 and X3 is nitrogen, wherein each of R1 and R2 isindependently selected from the group consisting of hydrogen, C1 to C10alkyl group and C6 to C30 aryl group, wherein R3 is cyano group, and R4is heteroaryl group, and wherein R5 is selected from the groupconsisting of hydrogen and heteroaryl group, and each of R6 and R7 ishydrogen or R6 and R7 are bonded together to form a fused ring.
 2. Thespace-through charge transfer compound according to claim 1, wherein Ais selected from Formula 4:


3. The space-through charge transfer compound according to claim 1,wherein D is selected from Formula 5:


4. The space-through charge transfer compound according to claim 1,wherein the space-through charge transfer compound is one of thefollowing compounds from Formula 6:


5. The space-through charge transfer compound according to claim 1,wherein a difference between an energy level of singlet state of thespace-through charge transfer compound and an energy level of tripletstate of the space-through charge transfer compound is less than about0.3 eV.
 6. An organic light emitting diode, comprising: a firstelectrode; a second electrode facing the first electrode; and a firstemitting material layer between the first and second electrodes, thefirst emitting material layer including a space-through charge transfercompound of claim
 1. 7. The organic light emitting diode according toclaim 6, wherein the first emitting material layer further includes afirst host, and the space-through charge transfer compound is used as adopant.
 8. The organic light emitting diode according to claim 7,wherein a difference between an energy level of a highest occupiedmolecular orbital (HOMO) of the first host and an energy level of a HOMOof the dopant or a difference between an energy level of a lowestunoccupied molecular orbital (LUMO) of the first host and an energylevel of a LUMO of the dopant is less than about 0.5 eV.
 9. The organiclight emitting diode according to claim 6, wherein the first emittingmaterial layer further includes a host and a first dopant, and thespace-through charge transfer compound is used as a second dopant, andwherein an energy level of singlet state of the second dopant is greaterthan an energy level of singlet state of the first dopant.
 10. Theorganic light emitting diode according to claim 9, wherein an energylevel of triplet state of the second dopant is smaller than an energylevel of triplet state of the host and greater than an energy level oftriplet state of the first dopant.
 11. The organic light emitting diodeaccording to claim 7, further comprising: a second emitting materiallayer including a second host and a first fluorescence dopant, whereinthe second emitting material layer is positioned between the firstelectrode and the first emitting material layer.
 12. The organic lightemitting diode according to claim 11, further comprising: an electronblocking layer between the first electrode and the second emittingmaterial layer, wherein a material of the second host is the same as amaterial of the electron blocking layer.
 13. The organic light emittingdiode according to claim 11, further comprising: a third emittingmaterial layer including a third host and a second fluorescent dopant,wherein the third emitting material layer is positioned between thesecond electrode and the first emitting material layer.
 14. The organiclight emitting diode according to claim 13, further comprising: a holeblocking layer between the second electrode and the third emittingmaterial layer, wherein a material of the third host is the same as amaterial of the hole blocking layer.
 15. The organic light emittingdiode according to claim 13, wherein an energy level of singlet state ofthe space-through charge transfer compound is greater than each of anenergy level of singlet state of the first fluorescent dopant and anenergy level of singlet state of the second fluorescent dopant.
 16. Theorganic light emitting diode according to claim 13, wherein an energylevel of singlet state and an energy level of triplet state of the firsthost is greater than an energy level of singlet state and an energylevel of triplet state of the space-through charge transfer compound,respectively, and wherein an energy level of singlet state of the secondhost is greater than an energy level of singlet state of the firstfluorescent dopant, and an energy level of singlet state of the thirdhost is greater than an energy level of singlet state of the secondfluorescent dopant.
 17. The organic light emitting diode according toclaim 11, wherein an energy level of singlet state of the space-throughcharge transfer compound is greater than an energy level of singletstate of the first fluorescent dopant.
 18. The organic light emittingdiode according to claim 11, wherein an energy level of singlet stateand an energy level of triplet state of the first host are greater thanan energy level of singlet state and an energy level of triplet state ofthe space-through charge transfer compound, respectively, and wherein anenergy level of singlet state of the second host is greater than anenergy level of singlet state of the first fluorescent dopant.
 19. Theorganic light emitting diode according to claim 6, wherein thespace-through charge transfer compound is one of the following compoundsfrom Formula 6:


20. An organic light emitting display device, comprising: a substrate;an organic light emitting diode of claim 6 disposed on the substrate;and an encapsulation film covering the organic light emitting diode.